This invention relates to a weft picking device of an air jet type weaving loom wherein a weft yarn is picked into the shed of warp yarns by the action of air jet, and more particularly to an improvement in a weft inserting nozzle of the weft picking device of the air jet type loom.
In conventional air jet type looms, picking of weft yarn has been carried out by ejecting air jet through an annular air ejection opening formed in a nozzle. The air ejection opening is usually formed around a weft introduction pipe of the nozzle through which the weft yarn is introduced into the nozzle. During picking operation, the weft yarn is dragged or pulled by the dragging force of the air jet from the nozzle, overcoming the resistances of a detaining device for detaining a certain length of the weft yarn required for each pick, of weft yarn guide members and of a grasping device for the weft yarn. In the conventional air jet type weaving looms of this nature, dragging of the weft yarn within and out the nozzle and subsequent carrying of the weft yarn are both achieved by the action of only an air jet of high pressure air. However, this causes drawbacks in which a considerably large amount of high pressure air is consumed and therefore electric power consumption for operation of the loom is increased.
Now, studying the mechanism of the picking of the weft yarn, the dragging force due to air jet is effective only at a high speed range lying within a distance of about 200 mm from the tip of the nozzle. Therefore, at a range remote from the high speed range, the dragging force is declined and accordingly only carrying of the weft yarn is mainly accomplished along the picking course of the weft yarn.
In view of the above, the inventor's attention has been paid to the fact that air jet of high pressure air is not always necessary throughout whole the picking operation of the weft yarn.